Fuel injection means for gas-turbine engines and combustion equipment used therewith



Jan. 25, 1955 F M JOHNSON ETAL 2,700,416

FUEL INJECTI ON MEANS FOR GAS-TURBINE ENGINES AND COMBUSTION EQUIPMENTUSED THEREWITH Filed April 10, 1950 2 Sheets-Sheet l i2 55% f 55 556 f5,v I a /1 fifll f6 V l lNl/LINTORS 1 FRZNCIQM. JOHNSON J DENIS R.CARLISLE Jan. 25, 1955 Filed April 10,

JOHNSON ET AL 2,700,416

FUEL INJECTIbN MEANS FOR GAS-TURBINE ENGINES AND COMBUSTION EQUIPMENTUSED THEREZWITH 1950 2 Sheets-Sheet 2 INUENTORS FRANCIS M mnnsqn *ozmsn. CARLISLE Arr urmsy;

United States Patent FUEL INJECTION lVIEANS FOR GAS-TURBINE ENGINES ANDCOMBUSTION EQUIPMENT USED THEREWITH Application April 10, 1950, SerialNo. 154,964

Claims priority, application Great Britain June 30, 1949 1 Claim. 01.158-'76) This invention relates to fuel injection means for gasturbineengines and combustion equipment used therewith. It is concerned with.fuel injection means of the kind which is located in a duct throughwhich air flows into the combustion chamber and by which fuel isintroduced into combustion equipment through an atomising orifice in theform of an atomised liquid spray.

Fuel injection means of this kind are extensively used in gas-turbineengines, a fuel supply from an external source being introduced into aswirl chamber, from which it emerges through an atomising orificeco-axial with the chamber.

Difficulties have been experienced with fuel injection means of thiskind due to incomplete combustion of the fuel in the combustionequipment tendingto cause carbon to be deposited on the face of theinjection means in which the atomising orifice is formed; such carbondeposits adversely aifect the production of uniformly atomised fuelspray. As a result, after extended periods of running of the engine,combustion efiiciency and uniformity of combustion have been found todeteriorate.

The primary object of the present invention is to provide an arrangementof fuel injection means in which such tendency to carbon formation isdecreased or obviated.

According to the present invention, fuel injection means of the kindspecified comprises an assembly of parts, whereof the nose portion ofthe assembly has a substantially conical exterior surface at the apex ofwhich the atomising orifice is provided to extend axially of the conicalsurface, said conical nose portion being surrounded over part of itsaxial length by a shroud element to define with the said conical surfacean annular passage into which cooling air is fed from the duct throughwhich the combustion air flows to the combustion chamber and from whichthe cooling air issues in a direction towards the axis of the orificeand so as to sweep the conical surface.

In one embodiment of the invention, the atomising orifice is formed in apart of the assembly which constitutes the nose portion of the fuelinjection means.

In certain cases the nose portion may be constituted by two separateconical surfaces of differing apical angles, of which the one of greaterapical angle has its smaller end of substantially the same diameter asthe larger end of the one of smaller apical angle, and which are soarranged that the conical surfaces form a substantially continuoussurface, the atomising orifice being formed in or being carried at theapex of the part of lesser apical angle. In such an arrangement, theshroud element may encircle the part of the nose having the largerapical angle and may be given an internal conical form similar to thesurface of greater apical angle thus to provide an annular convergentpassage from which a cooling air flow issues to sweep over the conicalsurface of lesser apical angle.

With the arrangement of the invention, the cooling air issuing from theannular passage is directed to pass over the surface of the part formedwith or supporting the atomising orifice to cool the latter, and byvirtue of its scouring action to prevent the deposition of carbon on theorifice part.

It should be mentioned that in constructions previ- 2,700,416 PatentedJan. 25, 1955 ously adopted the exterior surface of the orifice part hasbeen in a plane substantially normal to the axis of the orifice, andcooling air for the injection device issued therefrom at a substantialangle to the plane of the exterior surface of the orifice part so thatit did not flow over this surface, and it is thought that this hascontributed to the difliculties outlined above.

In fuel injection means according to the invention the shroudsurrounding the nose portion to provide the annular passage isconveniently formed as an element of the injection means, i. e. theshroudelement forms part of the assembly of the injection means to beremoved and installed therewith. Alternatively the shroud may beconstituted by an element of the combustion equipment.

In a preferred embodiment of the invention one shroud element surroundsthe nose portion and constitutes an item "of the fuel injection means,whilst an additional part of the combustion equipment surrounds the fuelinjection means and defines with the external surface of the shroudelement a second annular passage from which air issues substantiallyparallel to the conical surface of the nose portion.

The invention may conveniently be used in combination with thearrangementdescribed in our co-pending application No. 154,965, filedApril 10, 1950, in which provision is made in combustion equipmentcomprising flame tubes for preventing carbon formation on the di vergentportion of a flame tube in the region of the fuel injection means.

Two embodiments of the invention will now be described, by way ofexample, with reference/to the accompanying drawings of which:

Figure 1 illustrates diagrammatically a gas turbine engme.

Figure 2 is a sectional view through a combustion chamber of such engineon an enlarged scale showing the fuel injection means, and

Figure 3 shows a modification of the fuel injection means.

The gas turbine engine shown in Figure 1 comprises a compressor 10delivering compressed air to combustion equipment 11, from which theproducts of combustion pass through a turbine 12, which drives thecompressor 10, and through a jet-pipe 13 with propelling nozzle 14 toatmosphere. The engine is suitable for aircraft jet propulsion.

The combustion equipment 11 comprises a plurality of substantiallytubular flame tubes accommodated within substantially tubular aircasings.

In Figure 2 one such air casing and flame tube is shown in section, thearrangement comprising an entry expansion chamber portion 15 which isconnected with the delivery side of the engine compressor 10, and is ofdivergent substantially circular cross section. The expansion chamber 15is connected by a bolted flange joint 16 with a tubular main air casingpart or structure 17, which in turn is connected at its outlet end witha nozzle entry assembly of the turbine 12.' Internally of'the air casing17 there is accommodated a generally tubular flame tube or flame tubestructure 18. The flame tube 18 is spaced from the wall of the aircasing 17 to form an annular duct 19 which extends into the expansionchamber 15 and provides a passage for the flow of mixing air into theflame tube. Within the expansion chamber' 15 is mounted air entry ductmeans comprising a divergent entry duct 20, the smaller end 20A of whichis directed towards the inlet end of the expansion chamber 15 to providea forward-facing air inlet, and this entry duct 20 divides the airentering the air casing 17 from the compressor system into a mixing airflow which passes into the annular duct 19 between the flame tube 18 andair casing 17 and into a primary air flow which passes through thedivergent entry duct 20 into the interior of the flame tube 18 at itsentry end. The divergent entry duct 20 is also formed at its downstreamend 20B with a spigot flange 21 which serves to support the flame tube18 at the outer radius, so that the entry duct 20 is in effect anextension of the flame tube 18 into the expansion chamber 15.

Fuel injection means generally indicated at 22 is supported within thedivergent entry duct to introduce fuel as. an. atomised. spray intovthe. interior. of the flame through connection 25. The fuel injectionmeans 22'.

further includes a swirl chamber. part 26 which defines a swirl chamber126 and an orifice plate 27 with orifice 27A through which the swirlchamber is adapted to inject fuel. The swirl chamber part 26 and orificeplate 27 are secured together axially as an assembly by a first nutmember 28, whilst this assembly is iecuregd axially to the bodypart by asecond nut mem- In accordance with the main feature of this inventionthe orifice plate 27 and first nut member 28 are formed with asubstantially conical exterior surface 361, which is coaxial with theorifice, so that the nose portion of the fuel injector 22 is of pointedform. Additionaliy a shroud part 29A is provided surrounding thisconical surface, to form an annular passage 31 between the surface 30and the shroud 29A.

The shroud 29A is constituted as part of the second nut member 29 andhas a cylindrical extension part 2913 surrounding the swirl chamber part26 and orifice plate 27. It will beseen that the cylindrical extension29B and conical shroud portion 29A are of greater diameter than theadjacent surface of the assembly comprising the swirl chamber part 26and orifice plate 27, so

as to provide an annular passage 31 for a flow of cooling air, whichpassage converges at its outlet end 31A. The cooling air enters theannular passage 31 from the space within the divergent entry duct 20through passage or aperture means comprising a number ofcircumferentially distributed holes 32 in the cylindrical extension 29Bof the clamping nut member, and issues from the convergent part 31A ofthe passage to flow along the unshrouded part of the conical surface 3%of the orifice plate towards the atomising orifice.

The clamping nut 29 is surrounded. by a part 33 of the flame tube 18,which part 33 has a cylindrical portion 33A and a convergent portion 33Bcorresponding in shape to the formof the external surface of the nut,thereby to form an annular passage or duct 34 around the fuel injectorassembly, through which passage cooling air passes from the interior ofthe divergent entry duct 20 into theinterior of the flame tube 18, thedirection of air flow at the outlet from this passage beingsubstantially parallel to the conical surface 30 of the orificeplatez27.

The arrangement provides that the unshrouded portion of the conicalsurface 30 of the orifice plate 27 and first nut member 28 is swept bythe flow of cooling air which does not diverge away from the surface 30,whilst the exterior surface of the clamping nut member 29 is cooled bythe flow through the annular passage34. It will be noted that the apicalangle of the portion of the conical surface 30 on the plate 27 is lessthan that of the portion of the surface 30 on the nut member 28, whicharrangement assists in the maintenance of the flow over the unshroudedportion of the surface 30.

In the modification shown in Figure 3 the fuel injection means comprisesa body portion with a fuel entry duct 46. The body portion 45accommodates.

a filter element 47, which is loaded by spring 48 and bears on swirl.plug, 49.. Anv orifice. 50 is formed. in an orifice part 51 the exteriorsurface 51A of which is substantially conical. The. orifice part 51 isclamped on to the body part by a nut element 52 having a cylindricalportion 53 and a flanged portion 54 which has a conical surface 54A.

A shroud element 55 is screwed on to the nut element 52 at. 55A, and isformed with a conical portion 553, thereby to constitute an annularpassage for the flow of cooling air which enters through passages 56. Inthis manner cooling air flows over the conical surfaces 54A and 51A.

rrangements inaccordance with the invention have been found effective toprevent the formation of carbon on the nose portion of the fuelinjection means assemblyv The invention can be applied to fuel injectionmeans of the kind comprising concentric atomising orifices, e. g. toarrangements in which a first (pilot) spray emerges through theatomising orifice used for a main fuel supply.

We claim:

In gas turbine combustion equipment of the kind including an air casingstructure, a flame tube structure accommodated in said air casingstructure, air entry duct means to saidfiame tube having aforward-facing air inlet, and fuel injector means mounted in said airentry duct means to. introduce fuel into said flame tube in theydirection of air flowing into said flame tube through. said' air entryduct means, the provision of fuelinjector means comprising means formingan atomising orifice joined to a swirl chamber part forming a swirlchamber adapted to inject fuel through said orilice, theexterior surfaceof said orifice forming means bounding saidi orifice being ofsubstantially conical form, said'exterior surface being surrounded overpart only of its axial length by a spaced annular shroud element whichis both internally and externally conical, whereby there is definedbetween said internal conical surface and the conical surfacesurrounding said atomising orifice an annular passage of conical form,there being additionally provided an annular part spaced from andsurrounding said shroud element and having an internally conicalsurface, said annular part and annular. shroudl defining an" annularduct connected to said annular passage by aperture means extendedthrough the wall of said. shroud and said annular duct having an airentry adapted to face the inlet of said entry duct'means, whereby air isabstracted from said entry ductmeans to, flow in. said annular duct inpart through said passage means to emerge along said conical surfacesurrounding the orifice and in part through the annular conical ductformed between the exterior conical surface of the shroud element andthe internal conical surface of the annular. part.

References Cited in the file of this patent UNITED STATES PATENTS1,740,296 Gerdes et al. Dec. 17, 1929 2,019,815 Holtham Nov. 5, 19352,022,513 Macchi Nov. 26, 1935 2,325,495 Ferguson July 27, 19432,411,181 Altorfer Nov. 19, 1946 2,414,442 Breault Ian. 21, 19472,483,951 Watson Oct. 4, 1949 2,574,879 Lundberg et a1. Nov. 13, 19512,595,759 Buckland et al. May 6, 1952

